Process for refining lead



Dec. 27, 1932. w. F. GROSS ET AL 1,891,973

PROCESS FOR REFINING LEAD Filed Jan. 22. 1927 gi genius N17475:? H JAM 7a,! ps8 351 M Que c1404;

Patented Dec. 27 1932 UNITED STATES PATENT OFFICE WALTER F. GROSS, 0]? ELIZABETH, AND CHARLES N. SAPPINGTON, OF PERTII AMBOY, NEW JERSEY, ASSIGNORS TO AMERICAN SMELTING AND REFINING COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY PROCESS FOR REFINING LEAD This invention relates to metal'refining and more particularly to a method of removng varlous impurities from the molten metal the surface thereof. The dross may be re; moved by skimming or other well known processes, leaving the remaining bullion substantially free from these elements and in a suitable condition for subsequent operations.

Copper, being commonly found in lead in objectionable quantities, is an important element to be removed therefrom. In order to remove this element as a dross it is necessary to use a drossing reagent capable of readily uniting therewith. The fact that other minor impurities may also be drossed by the reagent is of secondary importance to the removal of copper, although the added advantage received by their removal should not be overlooked.

Since sulphur is capable -Of drossing the copper and in addition will dross arsenic, selenium and tellurium, it has been found advisable to utilize this element in the pnrification of lead bullion. When uncombined sulphur is utilized a complex dross is.

cordance with the present invention by re moving a portion of the bullion from the bath and passing it in a flowing stream through a reaction box where a predetermined amount of reagent is added thereto. The stream is then returned to the kettle.

A suitable apparatus for carrying on this process has been disclosed herein by way of illustration only, it not being essential to'the success of this invention that such an appa ratus be used provided suitable means be employed for controlling the temperature of the bath and for depositing the reagent on the flowing stream of the metal and subsequently returning this stream to the kettle.

The apparatus herein disclosed comprises a pump by means of which the metal is pumped from the bottom of the kettle and passed through a reaction box wherein the required reaction takes place, suitable means being provided for adding the reagent to the flowing stream and returning the stream to the kettle.

The rate of flow of the bullion through the reaction box and the quantity of reagent added may be accurately controlled, the desired proportions being determined by the known copper content of the bullion.

In carrying on a process in tliis manner it is unnecessary to add an excess of reagent metal is assured. Having determined the quantity required to dross the copper content of the lead'bullion, it is only necessary to add that amount in order to substantially and completely remove the copper.

Although the novel features which are believed to be characteristic of this invention will be pointed out with particularity in' the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation and the manner of its organication may be better understood by referring to the following description taken in connection with the accompanying drawing forming a'part thereof, in which the figure is a diagrammatic showing of one form of apparatus which may be employed in carrying on this process. Y

In the following description and in the 80 since a complete contact with the stream of claims parts will be identified by specific names for convenience, but they are intended to be as generic in this application to similar parts as the art will ermit.

Referring to the gure more in detail, a bath of lead bullion is shown substantially filling a kettle 1 to which heat may be applied from a furnace or other suitable means (not shown). The refining apparatus comprises a motor 2 supported in a housing or framework 3 and carried by beams 4 which may rest upon the edges of kettle 1. Depending from the motor and extending substantially to the bottom of the kettle is a shaft 5. At the lower portion of this shaft and connected thereto is a"centrifugal pump 6, the rotary portion of the pum being driven by motor 2 through shaft 5. uitable bracing means 7 may be provided for firmly supporting the shaft while allowing free rotation thereof.

Pump 6 is adapted to force bullion from the bottom of kettle 1 through pipe 8 to suitable reaction box 10. Said reaction box may be supported upon beams 4 in which case the entire apparatus may be moved as a unit or 1t may be supported in any other desired manner. Box 10 is provided with an inlet opening 11 through which the molten metal from pipe 8 is received and a discharge openlng 12. Outlet pipe 13 may receive the metal flowing through opening 12 and discharge the same 'a suitable distance below the surface of the bath in kettle 1.

Means such as hopper 15 may be provided for carrying a supply of the reagent and controlling the amount thereof which is added to the reaction box. Hopper 15 may include valve mechanism 16 at its lower end for controlling the flow or reagent which is preferably introduced continuous'lv into the stream of molten metal although it may be added intermittentlv if desired. s

In carrying on this process the entire assembly, including the pump, motor-and reaction box, is placed upon and supported by the kettle. The pump may then be started causing the molten metal to flow in a continuous stream through pipe 8 to the reactionbox 10 and after passing through the box to be discharged again into the bath within the kettle through discharge pipe 13. During this process the valve 16 may be opened and the reagent, such as sulphur, allowed to flow into the reaction box where it is taken up by the flowing metal.

By introducing the reagent into the reaction box, the reaction takes place at that point making unnecessary the artificial agitation of the metal within the kettle.

It has been found that in certain forms of this apparatus lead bullion could be pumped through the reaction box at a. rate of about 4 tons per minute, 2 pounds of sulphur being added during the same interval of time. When the reaction took place at this rate, it required approximately one hour to completely treat 100 tons of metal.

The sulphur will react with the copper and the various other impurities which are present in minor quantities such as arsenic, selenium and tellurium, and cause them to form adross which floats upon the surface. The dross may be removed and utilized in any well known manner, any lead which is contained therein being subsequently recovered if desired.

The invention is herein described as applied to lead refining, various impurities such as copper, arsenic, selenium and tellurium being removed in the form of dross by the addition of suitable quantities of sulphur. It is, however, applicable to other processes in which it is desired to add a reagent to molten metal at a predetermined rate while insuring an intimat contact of the reagent with the metal.

Although certain novel features of the invention have been shown and described and have been pointed out in the annexed claims, it will be understood that various omissions,

substitutions and changes in the several steps of the process and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is: 1. The process of refining lead contaminated with copper which comprises forming a. molten bath of such lead, continuously removing a portion of the molten lead fromv said bath and causing said portion to flow externally of said bath in a thin stream having an exposed surface, adding sulphur to said surface at a rate to produce the desired re'action, and returning the products of reaction I by to substantially prevent oxidation of said sulphur.

In testimony whereof we have hereunto set our hands.

WALTER F. GROSS. CHARLES N. SAPPINGTON. 

